Topological correction of hypertextured implicit surfaces for ray casting

Hypertextures are a useful modelling tool in that they can add three-dimensional detail to the surface of otherwise smooth objects. Hypertextures can be rendered as implicit surfaces, resulting in objects with a complex but well defined boundary. However, representing a hypertexture as an implicit surface often results in many small parts being detached from the main surface, turning an object into a disconnected set. Depending on the context, this can detract from the realism in a scene where one usually does not expect a solid object to have clouds of smaller objects floating around it. We present a topology correction technique, integrated in a ray casting algorithm for hypertextured implicit surfaces, that detects and removes all the surface components that have become disconnected from the main surface. Our method works with implicit surfaces that are C2 continuous and uses Morse theory to find the critical points of the surface. The method follows the separatrix lines joining the critical points to isolate disconnected components

Texturing and hypertexturing of volumetric objects

ABSTRACT Texture mapping is an extremely powerful and flexible tool for adding complex surface detail to an object. This paper introduces a method of surface texturing and hypertexturing complex volumetric objects in real-time. We employ distance field volume representations, texture based volume rendering and procedural texturing techniques with Shader Model 2.0 flexible programmable graphics hardware. We aim to provide a flexible cross-platform, non vendor specific implementation

Implementation of a Functionally Gradient Material Modeling and Design System

New advancements in Solid Freeform Fabrication (SFF) processes promise the capability to produce Functionally Gradient Material (FGM) parts, in which the material compositions vary spatially. To realize this potential there is a need for CAD methods and design software to model, design, represent and exchange material information and instructions to the manufacturing process. However, currently available commercial CAD systems are limited to representing and storing only geometric information, which is not adequate for material design purposes. This work presents an extension of a theoretical approach based on Volumetric MultiTexturing (VMT) and hypertexturing schemes to make the material design process intuitive and user controllable. Inverse distance weighted interpolation is used in conjunction with procedural material functions to accomplish axial or linear material gradient directions from surface to surface across a solid. This offers the capability of specifying fixed material composition values to the faces in the solid and blending them across the interior of the solid. The extension of the proposed approach to the modeling of discrete material domains is also discussed. These material regions can be combined using special sets of operators depending on the form of the material functions. Finally, a design environment has been developed, which allows users to systematically apply material information to geometry and captures design intent.Mechanical Engineerin

Functionally Gradient Material Design and Modeling Using Hypertexture for Solid Freeform Fabrication

SFF technologies have the potential to become manufacturing process that are capable of producing parts that have not been feasible by other techniques. The fabrication of Functionally Gradient Material (FGM) is one of the possible candidate. It is critical.to provide three dimensional material gradient data in the solid model to fabricate FGM. The approach is to model spatially varying material density distribution on implicit solid geometry using a hypertexturing scheme and a procedural volumetric modeling. It is essentially an extension of procedural solid texture synthesis, which has been effectively used to model cloud, gas, and flow stream. It will save the amount of information storage especially when the gradient pattern is repeating. Geometric operation becomes convenient since the material data are linked to the geometry only by the reference surfaces.Mechanical Engineerin

Volume ray casting techniques and applications using general purpose computations on graphics processing units

Traditional 3D computer graphics focus on rendering the exterior of objects. Volume rendering is a technique used to visualize information corresponding to the interior of an object, commonly used in medical imaging and other fields. Visualization of such data may be accomplished by ray casting; an embarrassingly parallel algorithm also commonly used in ray tracing. There has been growing interest in performing general purpose computations on graphics processing units (GPGPU), which are capable exploiting parallel applications and yielding far greater performance than sequential implementations on CPUs. Modern GPUs allow for rapid acceleration of volume rendering applications, offering affordable high performance visualization systems. This thesis explores volume ray casting performance and visual quality enhancements using the NVIDIA CUDA platform, and demonstrates how high quality volume renderings can be produced with interactive and real time frame rates on modern commodity graphics hardware. A number of techniques are employed in this effort, including early ray termination, super sampling and texture filtering. In a performance comparison of a sequential versus CUDA implementation on high-end hardware, the latter is capable of rendering 60 frames per second with an impressive price-performance ratio heavily favoring GPUs. A number of unique volume rendering applications are explored including multiple volume rendering capable of arbitrary placement and rigid volume registration, hypertexturing and stereoscopic anaglyphs, each greatly enhanced by the real time interaction of volume data. The techniques and applications discussed in this thesis may prove to be invaluable tools in fields such as medical and molecular imaging, flow and scientific visualization, engineering drawing and many others

Hardware accelerated volume texturing.

The emergence of volume graphics, a sub field in computer graphics, has been evident for the last 15 years. Growing from scientific visualization problems, volume graphics has established itself as an important field in general computer graphics. However, the general graphics fraternity still favour the established surface graphics techniques. This is due to well founded and established techniques and a complete pipeline through software onto display hardware. This enables real-time applications to be constructed with ease and used by a wide range of end users due to the readily available graphics hardware adopted by many computer manufacturers. Volume graphics has traditionally been restricted to high-end systems due to the complexity involved with rendering volume datasets. Either specialised graphics hardware or powerful computers were required to generate images, many of these not in real-time. Although there have been specialised hardware solutions to the volume rendering problem, the adoption of the volume dataset as a primitive relies on end-users with commodity hardware being able to display images at interactive rates. The recent emergence of programmable consumer level graphics hardware is now allowing these platforms to compute volume rendering at interactive rates. Most of the work in this field is directed towards scientific visualisation. The work in this thesis addresses the issues in providing real-time volume graphics techniques to the general graphics community using commodity graphics hardware. Real-time texturing of volumetric data is explored as an important set of techniques in delivering volume datasets as a general graphics primitive. The main contributions of this work are; The introduction of efficient acceleration techniques; Interactive display of amorphous phenomena modelled outside an object defined in a volume dataset; Interactive procedural texture synthesis for volume data; 2D texturing techniques and extensions for volume data in real-time; A flexible surface detail mapping algorithm that removes many previous restrictions Parts of this work have been presented at the 4th International Workshop on Volume Graphics and also published in Volume Graphics 2005

An Image-Based Approach for Stochastic Volumetric and Procedural Details

International audienceNoisy volumetric details like clouds, grounds, plaster, bark, roughcast, etc. are frequently encountered in nature and bring an important contribution to the realism of outdoor scenes. We introduce a new interactive approach, easing the creation of procedural representations of “stochastic” volumetric details by using a single example photograph. Instead of attempting to reconstruct an accurate geometric representation from the photograph, we use a stochastic multi-scale approach that fits parameters of a multi-layered noise-based 3D deformation model, using a multi-resolution filter banks error metric. Once computed, visually similar details can be applied to arbitrary objects with a high degree of visual realism, since lighting and parallax effects are naturally taken into account. Our approach is inspired by image-based techniques. In practice, the user supplies a photograph of an object covered by noisy details, provides a corresponding coarse approximation of the shape of this object as well as an estimated lighting condition (generally a light source direction). Our system then determines the corresponding noise-based representation as well as some diffuse, ambient, specular and semi-transparency reflectance parameters. The resulting details are fully procedural and, as such, have the advantage of extreme compactness, while they can be infinitely extended without repetition in order to cover huge surfaces

Data model and software prototype for antenna geometrical information

The standard electromagnetic language EDX is formed by three parts.One is a set of Electromagnetic Data Dictionaries, establishing the lexicon. This work concern the develpment of the Structure Data Dictionary, including all the geometrical information and the related physical details.In parallel a Python-based prototype tool, was created. This is able to manage the physical structure data model theoretically developed and has been exploited to generate some complex examples up to full satellitesope

Survey of texture mapping techniques for representing and rendering volumetric mesostructure

Representation and rendering of volumetric mesostructure using texture mapping can potentially allow the display of highly detailed, animated surfaces at a low performance cost. Given the need for consistently more detailed and dynamic worlds rendered in real-time, volumetric texture mapping now becomes an area of great importance.In this survey, we review the developments of algorithms and techniques for representing volumetric mesostructure as texture-mapped detail. Our goal is to provide researchers with an overview of novel contributions to volumetric texture mapping as a starting point for further research and developers with a comparative review of techniques, giving insight into which methods would be fitting for particular tasks.We start by defining the scope of our domain and provide background information regarding mesostructure and volumetric texture mapping. Existing techniques are assessed in terms of content representation and storage as well as quality and performance of parameterization and rendering. Finally, we provide insights to the field and opportunities for research directions in terms of real-time volumetric texture-mapped surfaces under deformation